Annotation of rpl/lapack/lapack/dptsv.f, revision 1.11
1.9 bertrand 1: *> \brief \b DPTSV
2: *
3: * =========== DOCUMENTATION ===========
4: *
5: * Online html documentation available at
6: * http://www.netlib.org/lapack/explore-html/
7: *
8: *> \htmlonly
9: *> Download DPTSV + dependencies
10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dptsv.f">
11: *> [TGZ]</a>
12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dptsv.f">
13: *> [ZIP]</a>
14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dptsv.f">
15: *> [TXT]</a>
16: *> \endhtmlonly
17: *
18: * Definition:
19: * ===========
20: *
21: * SUBROUTINE DPTSV( N, NRHS, D, E, B, LDB, INFO )
22: *
23: * .. Scalar Arguments ..
24: * INTEGER INFO, LDB, N, NRHS
25: * ..
26: * .. Array Arguments ..
27: * DOUBLE PRECISION B( LDB, * ), D( * ), E( * )
28: * ..
29: *
30: *
31: *> \par Purpose:
32: * =============
33: *>
34: *> \verbatim
35: *>
36: *> DPTSV computes the solution to a real system of linear equations
37: *> A*X = B, where A is an N-by-N symmetric positive definite tridiagonal
38: *> matrix, and X and B are N-by-NRHS matrices.
39: *>
40: *> A is factored as A = L*D*L**T, and the factored form of A is then
41: *> used to solve the system of equations.
42: *> \endverbatim
43: *
44: * Arguments:
45: * ==========
46: *
47: *> \param[in] N
48: *> \verbatim
49: *> N is INTEGER
50: *> The order of the matrix A. N >= 0.
51: *> \endverbatim
52: *>
53: *> \param[in] NRHS
54: *> \verbatim
55: *> NRHS is INTEGER
56: *> The number of right hand sides, i.e., the number of columns
57: *> of the matrix B. NRHS >= 0.
58: *> \endverbatim
59: *>
60: *> \param[in,out] D
61: *> \verbatim
62: *> D is DOUBLE PRECISION array, dimension (N)
63: *> On entry, the n diagonal elements of the tridiagonal matrix
64: *> A. On exit, the n diagonal elements of the diagonal matrix
65: *> D from the factorization A = L*D*L**T.
66: *> \endverbatim
67: *>
68: *> \param[in,out] E
69: *> \verbatim
70: *> E is DOUBLE PRECISION array, dimension (N-1)
71: *> On entry, the (n-1) subdiagonal elements of the tridiagonal
72: *> matrix A. On exit, the (n-1) subdiagonal elements of the
73: *> unit bidiagonal factor L from the L*D*L**T factorization of
74: *> A. (E can also be regarded as the superdiagonal of the unit
75: *> bidiagonal factor U from the U**T*D*U factorization of A.)
76: *> \endverbatim
77: *>
78: *> \param[in,out] B
79: *> \verbatim
80: *> B is DOUBLE PRECISION array, dimension (LDB,NRHS)
81: *> On entry, the N-by-NRHS right hand side matrix B.
82: *> On exit, if INFO = 0, the N-by-NRHS solution matrix X.
83: *> \endverbatim
84: *>
85: *> \param[in] LDB
86: *> \verbatim
87: *> LDB is INTEGER
88: *> The leading dimension of the array B. LDB >= max(1,N).
89: *> \endverbatim
90: *>
91: *> \param[out] INFO
92: *> \verbatim
93: *> INFO is INTEGER
94: *> = 0: successful exit
95: *> < 0: if INFO = -i, the i-th argument had an illegal value
96: *> > 0: if INFO = i, the leading minor of order i is not
97: *> positive definite, and the solution has not been
98: *> computed. The factorization has not been completed
99: *> unless i = N.
100: *> \endverbatim
101: *
102: * Authors:
103: * ========
104: *
105: *> \author Univ. of Tennessee
106: *> \author Univ. of California Berkeley
107: *> \author Univ. of Colorado Denver
108: *> \author NAG Ltd.
109: *
110: *> \date November 2011
111: *
112: *> \ingroup doubleOTHERcomputational
113: *
114: * =====================================================================
1.1 bertrand 115: SUBROUTINE DPTSV( N, NRHS, D, E, B, LDB, INFO )
116: *
1.9 bertrand 117: * -- LAPACK computational routine (version 3.4.0) --
1.1 bertrand 118: * -- LAPACK is a software package provided by Univ. of Tennessee, --
119: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.9 bertrand 120: * November 2011
1.1 bertrand 121: *
122: * .. Scalar Arguments ..
123: INTEGER INFO, LDB, N, NRHS
124: * ..
125: * .. Array Arguments ..
126: DOUBLE PRECISION B( LDB, * ), D( * ), E( * )
127: * ..
128: *
129: * =====================================================================
130: *
131: * .. External Subroutines ..
132: EXTERNAL DPTTRF, DPTTRS, XERBLA
133: * ..
134: * .. Intrinsic Functions ..
135: INTRINSIC MAX
136: * ..
137: * .. Executable Statements ..
138: *
139: * Test the input parameters.
140: *
141: INFO = 0
142: IF( N.LT.0 ) THEN
143: INFO = -1
144: ELSE IF( NRHS.LT.0 ) THEN
145: INFO = -2
146: ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
147: INFO = -6
148: END IF
149: IF( INFO.NE.0 ) THEN
150: CALL XERBLA( 'DPTSV ', -INFO )
151: RETURN
152: END IF
153: *
1.8 bertrand 154: * Compute the L*D*L**T (or U**T*D*U) factorization of A.
1.1 bertrand 155: *
156: CALL DPTTRF( N, D, E, INFO )
157: IF( INFO.EQ.0 ) THEN
158: *
159: * Solve the system A*X = B, overwriting B with X.
160: *
161: CALL DPTTRS( N, NRHS, D, E, B, LDB, INFO )
162: END IF
163: RETURN
164: *
165: * End of DPTSV
166: *
167: END
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